-LRB- CNN -RRB- -- One night in late July this year , the Japanese supertanker M. Star was making its way through the Strait of Hormuz -- the chokepoint at the southern tip of the Persian Gulf . It was en route to Japan with 3 million barrels of crude oil .

There was a loud thud at the front of the ship . Its hull suffered a substantial square-shaped dent above the waterline . Theories about the cause quickly abounded : a giant wave , a collision with a submarine or another vessel . And then -- six days later -- a militant Sunni group that had been active in Lebanon , Egypt and Jordan claimed it had attacked the ship with an explosives-laden boat .

The Abdullah Azzam Brigades said the attack on the M. Star `` sought to weaken the infidel global order which is thrust into Muslim lands and which loots its resources . '' For the Brigades , such an attack was a significant departure from previous targets .

To begin with , intelligence analysts were skeptical of the claim . But U.S. officials now say it is credible .

`` Government and industry sources can confirm that the claim by the Abdullah Azzam brigades ... is valid , '' the U.S. Department of Transportation 's Maritime Administration said in an advisory last week .

`` The group remains active and can conduct further attacks on vessels in areas in the Strait of Hormuz , southern Arabian Gulf , and western Gulf of Oman , ' it said .

The Saudis are already anxious about the foothold that al Qaeda has established in neighboring Yemen . Now the Brigades -- spawned in the squalor of Palestinian refugee camps in Lebanon -- may be an emerging player in the region 's terror landscape .

The Brigades are named after a Palestinian close to al Qaeda leader Osama bin Laden . Abdullah Azzam was killed in Pakistan in 1989 by a bomb explosion .

The group is led by one Saleh al-Qarawi , who fought U.S. forces in Iraq and got to know al Qaeda 's now-dead leader there -- Abu Musab al-Zarqawi .

Born in the Saudi city of Barida , al-Qarawi is only 28 , but is already on the kingdom 's most wanted list . When that list was first published in February 2008 , he was described as `` one of the key suppliers of facilities , finances , fake documents '' for al Qaeda . And he has ambitious aims , telling an extremist website earlier this year : `` All the jihadist battlefields now are fields of fighting . ''

The Brigades have certainly shown themselves capable of audacious attacks . They claimed responsibility for an unsuccessful rocket attack on a U.S. warship anchored in the Jordanian port of Aqaba in 2005 , as well as for bombings in 2004 and 2005 aimed at tourists in Egypt 's Red Sea resorts . Well over 100 people were killed in those attacks .

In the interview he gave to the al-Fajr Media Center , al-Qarawi described how al-Zarqawi had sent him on a mission beyond Iraq . He 'd been arrested in Syria and spent a brief spell in a Saudi jail .

Describing his priorities , al-Qarawi said they include kidnapping U.S. and British citizens in the Arabian peninsula . `` American interests are our most important aims , '' he said , according to a translation by intelligence website Flashpoint Partners .

It is also clear from the interview that al-Qarawi is very much a Sunni purist . He has little time for the Shiite Hezbollah , accusing it of attacking Lebanon 's Sunnis . He also accuses Lebanese Shiites of `` malice '' toward the country 's Sunnis .

That suggests the Brigades would not have looked to Shiite Iran for help or harbor in attacking the M. Star -LRB- even if Saudi officials insist al-Qarawi once operated from Iran . -RRB-

And it prompts this question : where did that small boat , laden with explosives , come from on the night of July 27 to attack the M. Star ?

If not Iran , did it set out under cover of darkness from the United Arab Emirates , Oman or even Saudi Arabia -- undetected by authorities ?

@highlight

The Abdullah Azzam Brigades may be an emerging player in the Persian Gulf landscape

@highlight

The militant Sunni group is named for a Palestinian close to Osama bin Laden

@highlight

The group claimed responsibility for an attack on a Japanese supertanker in July